content: /*
   * Copyright (C) 2015 Square, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package hu.akarnokd.rxjava3.retrofit;
  
  import java.io.IOException;
  import java.lang.annotation.Annotation;
  import java.lang.reflect.*;
  
  import io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.*;
  import retrofit2.*;
  import retrofit2.HttpException;
  
  /**
   * A {@linkplain retrofit2.CallAdapter.Factory call adapter} which uses RxJava 3 for creating observables.
   * <p>
   * Adding this class to {@link Retrofit} allows you to return an {@link Observable},
   * {@link Flowable}, {@link Single}, {@link Completable} or {@link Maybe} from service methods.
   * <pre><code>
   * interface MyService {
   *   &#64;GET("user/me")
   *   Observable&lt;User&gt; getUser()
   * }
   * </code></pre>
   * There are three configurations supported for the {@code Observable}, {@code Flowable},
   * {@code Single}, {@link Completable} and {@code Maybe} type parameter:
   * <ul>
   * <li>Direct body (e.g., {@code Observable<User>}) calls {@code onNext} with the deserialized body
   * for 2XX responses and calls {@code onError} with {@link HttpException} for non-2XX responses and
   * {@link IOException} for network errors.</li>
   * <li>Response wrapped body (e.g., {@code Observable<Response<User>>}) calls {@code onNext}
   * with a {@link Response} object for all HTTP responses and calls {@code onError} with
   * {@link IOException} for network errors</li>
   * <li>Result wrapped body (e.g., {@code Observable<Result<User>>}) calls {@code onNext} with a
   * {@link Result} object for all HTTP responses and errors.</li>
   * </ul>
   */
  public final class RxJava3CallAdapterFactory extends CallAdapter.Factory {
    /**
     * Returns an instance which creates synchronous observables that do not operate on any scheduler
     * by default.
     * @return the new adapter instance
     */
    public static RxJava3CallAdapterFactory create() {
      return new RxJava3CallAdapterFactory(null, false);
    }
  
    /**
     * Returns an instance which creates asynchronous observables. Applying
     * {@link Observable#subscribeOn} has no effect on stream types created by this factory.
     * @return the new adapter instance
     */
    public static RxJava3CallAdapterFactory createAsync() {
      return new RxJava3CallAdapterFactory(null, true);
    }
  
    /**
     * Returns an instance which creates synchronous observables that
     * {@linkplain Observable#subscribeOn(Scheduler) subscribe on} {@code scheduler} by default.
     * @param scheduler the scheduler to run the network operations on
     * @return the new adapter instance
     */
    public static RxJava3CallAdapterFactory createWithScheduler(Scheduler scheduler) {
      if (scheduler == null) throw new NullPointerException("scheduler == null");
      return new RxJava3CallAdapterFactory(scheduler, false);
    }
  
    private final @Nullable Scheduler scheduler;
    private final boolean isAsync;
  
    private RxJava3CallAdapterFactory(@Nullable Scheduler scheduler, boolean isAsync) {
      this.scheduler = scheduler;
      this.isAsync = isAsync;
    }
  
    @Override public @Nullable CallAdapter<?, ?> get(
        Type returnType, Annotation[] annotations, Retrofit retrofit) {
      Class<?> rawType = getRawType(returnType);
  
      if (rawType == Completable.class) {
        // Completable is not parameterized (which is what the rest of this method deals with) so it
        // can only be created with a single configuration.
        return new RxJava3CallAdapter<>(Void.class, scheduler, isAsync, false, true, false, false,
            false, true);
      }
  
      boolean isFlowable = rawType == Flowable.class;
      boolean isSingle = rawType == Single.class;
      boolean isMaybe = rawType == Maybe.class;
      if (rawType != Observable.class && !isFlowable && !isSingle && !isMaybe) {
        return null;
      }
  
      boolean isResult = false;
      boolean isBody = false;
      Type responseType;
      if (!(returnType instanceof ParameterizedType)) {
        String name = isFlowable ? "Flowable"
            : isSingle ? "Single"
            : isMaybe ? "Maybe" : "Observable";
        throw new IllegalStateException(name + " return type must be parameterized"
            + " as " + name + "<Foo> or " + name + "<? extends Foo>");
      }
  
      Type observableType = getParameterUpperBound(0, (ParameterizedType) returnType);
      Class<?> rawObservableType = getRawType(observableType);
      if (rawObservableType == Response.class) {
        if (!(observableType instanceof ParameterizedType)) {
          throw new IllegalStateException("Response must be parameterized"
              + " as Response<Foo> or Response<? extends Foo>");
        }
        responseType = getParameterUpperBound(0, (ParameterizedType) observableType);
      } else if (rawObservableType == Result.class) {
        if (!(observableType instanceof ParameterizedType)) {
          throw new IllegalStateException("Result must be parameterized"
              + " as Result<Foo> or Result<? extends Foo>");
        }
        responseType = getParameterUpperBound(0, (ParameterizedType) observableType);
        isResult = true;
      } else {
        responseType = observableType;
        isBody = true;
      }
  
      return new RxJava3CallAdapter<>(responseType, scheduler, isAsync, isResult, isBody, isFlowable,
          isSingle, isMaybe, false);
    }
  }
  